Skull clamp



FIG. 1 is a perspective view of a skull clamp showing our new design;

FIG. 2 is an end view thereof from the left side as shown in FIG. 1;

FIG. 3 is a top view of the skull clamp;

FIG. 4 is a side view of the skull clamp;

FIG. 5 is an end view thereof from the right side as shown in FIG. 1;

FIG. 6 is an inverted side view of the skull clamp of FIG. 4; and,

FIG. 7 is a bottom view thereof. 

We claim the ornamental design for the skull clamp, as shown and described. 